A conventional pottery planter is shown in FIGS. 1 and 2. The pottery planters 10 often comprise a wide, thick peripheral rim 12 at the upper edge of the planter. The wide rim has a pleasing appearance and provides a comfortable grip for lifting and moving the planter. The interior 14 of the rim of the pottery planter is solid, that is, the rim is filled with the clay material.
Planters formed of thermoplastic material provide advantages over pottery planters. A plastic planter is lighter, easier to handle, and less expensive to manufacture. Plastic planters can be produced in various colors and surface finishes more easily than a comparable ceramic planter.
But problems arise when trying to replicate the design of FIGS. 1 and 2 with plastic material. The mass of a thick rim of solid plastic makes cooling problematic—after the rest of the plastic material has cooled, the rim is still hot and can sag or deform before it solidifies. But the plastic within the solid rim is not necessary either structurally or aesthetically, and costs can be reduced if the amount of material needed to form the planter is reduced.
One way of addressing these issues would be to make the rim hollow. U.S. Pat. No. 6,383,440 to Chen discloses a one-piece plastic container with an integral hollow rim. As shown in FIG. 8 of Chen, the container 72 includes integral rim walls 74, 75 defining a hollow space 76. However, the container disclosed in Chen requires a complex manufacturing process involving expensive equipment comprising a series of active and passive dies and the blowing of air into a die chamber to form the hollow space within the rim.